The global demand for edible proteins is increasing steadily, propelled by the growing world population. This trend is further reinforced by the increasing income per capita in developing countries. Multiple studies indicate the advantage of using plant proteins, i.e. proteins derived from source materials of vegetable origin, as vital component in the human diet. The production of plant protein is typically more sustainable than that of animal protein in terms of greenhouse gas emissions and the use of scarce resources like land, water and energy. An increase in the use of plant proteins would therefore significantly contribute to more sustainable protein supply in the future.
Main sources of plant proteins are legumes such as soy beans, peas, faba beans, oil seeds such as rape seed, sunflower and cereals such as wheat and maize. To increase the use of plant proteins in human diet, methods of isolation of the proteins from plants need to be developed and deployed on industrial scale. The challenge is to obtain (edible) protein isolates with high purity (i.e. low in fat content and free from anti-nutritional factors) and with preserved desirable functional properties of the protein such as solubility, ability to form stable foams, ability to form gels, and water-absorbing and fat-absorbing ability and capacity.
Prior art technology for removal of endogenous oils and lipids from crude vegetable protein sources such as oilseeds usually implies use of low boiling organic solvents such as butane or hexane. Residuals of such solvents in the remaining protein-rich fraction of the crude vegetable protein source after oil/lipid extraction, have to be removed subsequently by use of heat in a purposely devised step, sometimes called desolventization—toasting, where high temperatures and steam are used to remove the solvent. Unfortunately, such harsh conditions may significantly limit the subsequent extractability and resulting functionality of the proteins. That is to say, the lipid/oil extraction methods commonly applied result in non-native proteins with low value to the food industry.
Subjecting vegetable protein source material, such as oilseed meal to hexane and desolventization-toasting results in irreversible interactions of proteins present in the source material with the anti-nutritional factors such as phenolic compounds and phytates. These interactions provide difficulties regarding removal of these anti-nutritional factors in the subsequent process of isolation of proteins.
Presence of fat in the vegetable protein source material poses a tremendous challenge to the processor, since the conventional technologies described in the prior art do not provide for an effective method of separating fat from proteinaceous components of the source material without compromising functional properties of the proteins.
If conventional techniques for extraction of proteins are applied, such as extensive mixing and agitating of source material with extraction solvent in a stirred vessel, oils and lipids typically co-extract with the proteins. Oils and lipids, when released from the source material during the extraction process, form emulsions that are stabilized by the proteins present in the source material. Applying technologies described in prior art for isolation of proteins such as those technologies used for processing of soy meals, results in concentration of fat together with the protein.
The fat present in the final isolate severely impairs the functionality of the protein as it can also lead to rancidity and other fat related problems, including poor solubility, caking as well as discoloration.
Patent application US 005844086A suggested a process concept to isolate proteins from oil cakes of canola having a fat content up to 10%, which process comprises steps such as: extraction proteins from canola cake in saline solution, pressing, centrifugation, fine filtration, ultrafiltration, combined with dilution and chilling of the intermediate process liquids to remove fatty layer by decantation. While such a process could potentially be applied to oilcakes that have not been treated with hexane, it does not provide the solution that could be readily implemented on industrial scale, due to the multi-step process. Also noteworthy is that the Murray process implies usage of traditional extraction techniques, thus including an extraction step using organic solvent and including a desolventization-toasting step.
In WO 2013/013949 a protein isolation process is provided for isolation of protein from oil cake comprising the steps of: extraction of proteins with aqueous solution, concentration and adding water-soluble organic solvent to obtain a protein precipitate. Extraction of the proteins is carried out by providing a suspension of a crude vegetable protein source in water and stirring the suspension The shear stress applied to a protein source by the stirring induces release of lipids from the source material and formation of stable emulsion of fats and proteins that is difficult to separate from the extract in the subsequent process steps. This phenomenon will be particularly severe when the conventional technique of extraction in the stirred vessel is applied on industrial scale, as it is known in the prior art that shear rates in the large scale stirred vessel reach levels of 100-1000 per second [Camperi A., et al., 2008; Carta G, Jungbauer, 2010].
In WO 2014/147068 a protein isolation process is provided for isolation of protein from oil cake comprising the steps of subjection oil seed meal to gravity induced solid-liquid extraction and optionally collecting the resulting intermediate aqueous protein solution. The multi-component system for isolation a protein fraction according to the process of WO 2014/147068 comprises 4 pump units and two containers. Relatively large volumes of aqueous solution are applied during the protein isolation process.
Current methods and devices all bear one or more of the drawbacks as exemplified above. Protein native conformation is not conserved when vegetable source material is subjected to a protein extraction process, in several conventional methods. Devices for a process of retrieving a protein extract from a vegetable sources are hard to scale up, or it has to be used in a laborious manner, requiring numerous components and a large volume of solvent, in several occasions. The field is thus demanding a scalable process and a suitable device for such scalable process, for preparing a protein extract comprising protein in its native conformation from vegetable sources such as oilseeds. The process should have gentle mild conditions leaving the native conformation of protein in the e.g. oilseed starting material intact. Ideally, the process consumes less solvent and ideally, the device comprises a limited number of components, i.e. tanks, pumps, etc.